A Proposal for Improvement of Smoke Detectors

Smoke detectors are used to warn people of hazards due to fire and smoke. When smoke is detected, an acoustic alarm signal is emitted. False alarms, which can be caused by component failures, are extremely undesirable, depending on the field of application. Therefore, this paper presents a concept developed according to the requirements of the generic safety standard IEC 61508:2010. The aim of this development is to avoid false alarms due to component failures and additionally to increase the availability of the safety function (smoke detection). This concept includes a fault detection system that can detect all random hardware failures and assign them to the channel in which they occur. This channel can then be deactivated and the remaining channel is able to keep the safety function alive until the system is repaired or replaced. Besides an introduction to the normative basics, the advantages of the newly developed safety architecture are described. Based on a comparison of the safety characteristics Average Probability of Dangerous Failure per Hour and Average Probability of Dangerous Failure on Demand, it is argued why the newly developed circuit has an advantage compared to classic structures. The long-term goal is to develop a smoke detector that meets all the requirements of IEC 61508:2010 (including the necessary measures for fault avoidance for hardware and software development). The results may be transferred to other control systems in general, which require a combination of high reliability and high availability at the same time.